Heat Pump to Hot Water Baseboards.

[RNeumann]

Interesting. The baseboards in this house are existing, pump, etc. I would have thought it would be simpler, no ugly through the wall units and no expensive ductwork to install.

I’m with you- I’d just use a propane or nat gas fired “boiler”. They are the size of a demand water heater (fairly small) and typically have a 90 plus percent efficiency rating. They make electric (resistive heat) ones too.

I know you can use a heat pump to make hot water......but I don’t think the juice is worth the squeeze.

 

[Tractor Seabee]

I’m with you- I’d just use a propane or nat gas fired “boiler”. They are the size of a demand water heater (fairly small) and typically have a 90 plus percent efficiency rating. They make electric (resistive heat) ones too.

I know you can use a heat pump to make hot water......but I don’t think the juice is worth the squeeze.

RN is on the track here. That is the best way to go just simply changing out the boiler to a modern condensing style. They are just a larger version of the "on demand domestic hot water heaters". Seems I have seen ones rated at 96-98%. Check out them on the internet. I would replace any auxiliary components and any pumps not part of the new boiler. Once a year have it serviced. The components are all break down maintenance items otherwise. If I had rentals I would want stuff as trouble free as possible unless it is high end enough that tenants want and will pay for fancy amenities.

Most manufacturers of heating equipment are dropping there inefficient type units. Then you have local jurisdictions like Seattle where they want to ban all CO2 emitting fuels. Funny thing they are just upping the CO2 produced making the electric power that replaces the other.

Oh the world we live in.

Ron

 

[dlctcg]

I would tend to agree with the condensing style boiler for this application, they are easily found with 92% + efficiency (98% not even out of the question) & it is probably how I would design the system. However just make sure it is sized properly or you will lose efficiency; do not just look at the existing oil boilers btu's & & purchase that size condensing boiler. (do not let any contractor do that for you either).

Condensing Boilers depend on lower return temps in order to be efficient, they will not go into condensation mode with to high of a return temperature so it is important they are sized correctly. Odds are you will need a lower sizes BTU boiler than what id currently there after calculations are done.

My main recommendation is to have a Heat Load Calculation done on the property prior to making any decisions. If done properly it will give you a very good idea of what your heat source sizing should be based on the construction of the property; taking into the fact any possible upgrades to insulation, window, etc. This would be my true starting point prior to making any decision; you may find a heat pump will work but do to actual heat load you can go with a smaller condensing boiler which lowers the price & complexity.

I substantially reduce our boiler size after a major remodel, which included insulation upgrades & retrofitting hydronic radiant floor heat throughout the entire house; I would not have know yo do this without a Heat Load Calculation... my .02

 

[fitter1]

All good feedback above. As for the baseboard most likely sized with 180 degree avg. water temp. Resetting water supply temp. based on outside air temp. will also save fuel.

 

[Tractor Seabee]

All good feedback above. As for the baseboard most likely sized with 180 degree avg. water temp. Resetting water supply temp. based on outside air temp. will also save fuel.

Great additions to the dialog by you and Dictcg. Cannot emphasize enough about the return water temp. A variable speed pump tied to the return side temp can keep the water in the fin coils long enough to wring the heat out . Another reason to size properly. A short cycling boiler will also delete a lot of the savings. Many systems are designed to also heat the domestic water also which adds a heat reservoir to reduce short recycling. Lennox used to make a boiler specifically designed for that not sure they still do. I installed a couple for my Kids and they worked great and economical, pretty trouble free even though they weren't too good on maintenance.

Because the finned pipe convectors were probably designed for 180 degree water they may now be under sized for a lower temp water supply (where the variable speed pump helps). Where he lives there may not be much advantage to an outdoor temp reset control. Many of the new boilers also have a turn down burner capability also. All in all still the cheapest install.

Ron

 

[dlctcg]

Tractor Seabee - Glad you brought up the variable speed pumps with return side temp... totally slipped my mind but definitely should be planned into the system.

I run 4 Taco Viridian Delta-T Variable Speed ECM High Efficiency Circulator pumps on my system which allow for temperature sensing on return & then variable speed circulation based on that temp & my set points ideal for Delta-T or set points. Glad you mentioned it.

Dennis

 

[Raspy]

One factor that may help you tip the scales in one direction or the other is to determine your heat load and the linear feet of baseboard you have. Then determine how many BTUs per foot your baseboards put out at 180 degrees and at 140 degrees. This number is all easily available in the manufacturer's information.

I never designed my systems to run at 180 degrees. They were all designed to do well at 140 degrees.

So if you can get good efficiency at the lower temps, and provide enough BTUs to the house with that temp, you might be more inclined to install the system you seem to want.

But even at 140 degrees, you'll be at lower efficiency than you would be at radiant floor temperatures.

So, is your priority low cost of operation, or low cost of installation? Who will be paying the energy bill?

 

[goeduck]

Great thoughts. Manuafacturer data might be hard to come by, the house was built in the 50s. Along with your lines of thinking, I may set the oil furnace down to 120 or 140 or so (assuming I can) this winter and see how it does without the wood stove running and put the upgrade off a year. It is really too late this year anyway. I had ditched the water to water heat pump idea after reading the input here in favor of either a couple of mini splits or a propane furnace but this might be an easy way to see how it does.

I should clarify, it is not a typical rental. We rent it out to extended family/friends and/or use it for family functions. So the priority is comfort and reliability. Cost is always a factor too. But this gives me an opportunity to know exactly how it performs if I stay overnight myself rather than just have input from a renter.

 

[dlctcg]

Some furnaces are not designed to run correctly (or efficiently) at 120 - 140 so just be cautious

If you find your system is not designed to run that low, you can still run 120 - 140 degree water through the radiators if you want to with a little creative plumbing. Our boiler at our camp is designed to run between 140 low point -185 high point which we have it set to; however we retrofitted the camp with radiant heat also, so we use a mixing valve to mix in some of the return water with the boiler water to get our temps down to a constant 120 -140 supplying the radiant. Pretty simple & not that expensive if your boiler is not designed to run that low... Just an option...

 

[RalphVa]

I have a rental house with an old oil furnace and hot water baseboard heaters that needs upgrading. Has anyone done an air to water heat pump or geo to water heat pump and then pumped the water to hot water baseboards?

They make hot water heaters now that use a heat pump with an electric coil backup. You could just put in a pump operated off a thermostat to pump that hot water to your baseboard heating elements. Of course, one of the benefits of a geothermal unit to heat your house is normally free hot water in a new hot water heater that runs off the discharge of the heat pump.

Ralph